The proposed program is for the development of an external, portable pneumatically coupled driver for use with pneumatically powered ventricular assist devices. The driver utilizes a long stroke piston mechanism to reduce motor torque requirements and associated motor weight. Pressure will be monitored continuously and used to predict VAD displacement. Prediction will be modeled based on basic thermodynamic principles, with empirically derived corrections. Displacement will be measured during VAD filling to retrospectively evaluate the ejection estimate. When a displacement transducer is provided as part of the pump design it will be used as an independent measure of pump displacement. VAD ejection will be controlled to reduce blood trauma, to prevent over- collapse of the VAD, and to improve system efficiency. PROPOSED COMMERCIAL APPLICATION: The device will be suitable for outpatient use with a variety of pneumatically powered ventricular assist devices. Such devices are nearing commercial availability. With the large discrepancy between those requiring some form of ventricular assistance and the number of available donor hearts, there is the potential for a very large market.